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  • Author or Editor: Xianjin Yu x
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Abstract  

Sorption and desorption of radioeuropium on red earth and its solid components to remove organic matter was studied at pH 5.3±0.1 and 4.5±0.1, and in 0.01M and 0.001M NaClO4 solutions, respectively. Eu(III) sorption showed strong pH and humic acid concentration dependency, and NaClO4 concentration independency. The sorption increased with increasing pH and amount of HA adsorbed on red earth. The sorption of Eu(III) on red earth was mainly dominated by surface complexation. Humic acid and high pH had a great tendency to immobilize the movement of Eu(III) in red earth. Sorption-desorption hysteresis of Eu(III) on red earth indicated that the sorption was irreversible.

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Abstract  

In this work, adsorption of Ni(II) from aqueous solution onto hematite under various solution chemistry and temperature was investigated. The results indicated that the pseudo-second-order rate equation fitted the kinetic adsorption well. The adsorption of Ni(II) onto hematite was strongly dependent on pH and ionic strength. At low pH, the adsorption was dominated by outer-sphere surface complexation or ion exchange, whereas inner-sphere surface complexation was the main adsorption mechanism at high pH. A positive effect of FA on Ni(II) adsorption was found at pH < 8.0, whereas a negative effect was observed at pH > 8.0. The Langmuir, Freundlich, and D–R models were applied to simulate the adsorption isotherms at three different temperatures of 293.15, 313.15 and 333.15 K. The thermodynamic parameters were calculated from the temperature dependent adsorption, and the results indicated that the adsorption was endothermic and spontaneous.

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Abstract  

The sorption of 63Ni(II) from aqueous solution using ZSM-5 zeolite was investigated by batch technique under ambient conditions. ZSM-5 zeolite was characterized by point of zero net proton charge (PZNPC) titration. The sorption was investigated as a function of shaking time, pH, ionic strength, foreign ions, humic acid (HA), fulvic acid (FA) and temperature. The results indicate that the sorption of 63Ni(II) on ZSM-5 zeolite is strongly dependent on pH. The sorption is dependent on ionic strength at low pH, but independent of ionic strength at high pH values. The presence of HA/FA enhances 63Ni(II) sorption at low pH values, whereas reduces 63Ni(II) sorption at high pH values. The sorption isotherms are simulated by Langmuir model very well. The thermodynamic parameters (i.e., ∆H 0, ∆S 0 and ∆G 0) for the sorption of 63Ni(II) are determined from the temperature dependent sorption isotherms at 293.15, 313.15 and 333.15 K, respectively, and the results indicate that the sorption process of 63Ni(II) on ZSM-5 zeolite is spontaneous and endothermic.

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Abstract  

The fate and transport of toxic metal ions and radionuclides in the environment is generally controlled by sorption reactions. The removal of 60Co(II) from wastewaters by MnO2 was studied as a function of various environmental parameters such as shaking time, pH, ionic strength, foreign ions, and humic substances under ambient conditions. The results indicated that the sorption of 60Co(II) on MnO2 was strongly dependent on pH and ionic strength. At low pH, the sorption of 60Co(II) was dominated by outer-sphere surface complexation and ion exchange with Na+/H+ on MnO2 surfaces, whereas inner-sphere surface complexation was the main sorption mechanism at high pH. The presence of HA/FA enhances 60Co(II) sorption at low pH values, whereas reduces 60Co(II) sorption at high pH values. The Langmuir and Freundlich models were used to simulate the sorption isotherms of 60Co(II) at three different temperatures of 298.15, 318.15 and 338.15 K. The thermodynamic parameters (ΔH 0, ΔS 0 and ΔG 0) calculated from the temperature dependent sorption isotherms indicated that the sorption process of 60Co(II) on MnO2 was endothermic and spontaneous.

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Abstract  

Sorption and desorption of Co(II) on montmorillonite under ambient conditions as a function of pH, ionic strength and fulvic acid are studied by batch technique. The results indicate that the sorption of Co(II) is dependent on pH, and ionic strength. The sorption-desorption hysteresis is found in the desorption tests. Surface complexation is considered as the main sorption mechanism of Co(II) on montmorillonite. The presence of fulvic acid (FA) enhances the sorption of Co(II) on montmorillonite. Montmorillonite is considered as a promising candidate for the solidification and pre-concentration of Co(II) from large volume of solutions.

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